import cv2
import numpy as np

lena=cv2.imread("3\\lena_gray.jpg")

x,y,z=lena.shape
lena2=np.zeros((x,y,z),dtype=np.uint8)
lena2[60:200,60:200]=255
lena2[120:256,40:100]=255
lena2[175:256,25:100]=255

lena3=cv2.bitwise_or(lena, lena2)

cv2.imshow("lena3",lena3)
cv2.waitKey()
cv2.destroyAllWindows()